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Main Page | Modules | Namespace List | Class Hierarchy | Alphabetical List | Class List | Directories | File List | Namespace Members | Class Members | File Members | Related Pages
Walker Class ReferenceA functional class to traverse an AST, and perform some function at each of its Nodes.
More...
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Public Types | |
enum | Order { Preorder, Postorder, Both } |
The order in which AST Nodes should be visited. More... | |
enum | Depth { Subtree, NodeOnly } |
Which Nodes in the AST tree should be visited. More... | |
Public Member Functions | |
Walker (Order the_order, Depth depth) | |
Create a new instance of a Walker. | |
Accessors | |
Methods to get and set fields in the class. | |
Order | order () const |
Return the order in which Nodes of an AST should be visited. | |
Depth | depth () const |
Return which Nodes of an AST should be visited. | |
"at_" methods | |
These methods define the functions that should be performed when different classes of Nodes are encountered in the AST. The most specific "at_" method that matches a given Node's class will be called. | |
virtual void | at_node (Node *the_node, Order ord) |
virtual void | at_unit (unitNode *the_unit, Order ord) |
virtual void | at_def (defNode *the_def, Order ord) |
virtual void | at_decl (declNode *the_decl, Order ord) |
virtual void | at_subdecl (subdeclNode *the_subdecl, Order ord) |
virtual void | at_proc (procNode *the_proc, Order ord) |
virtual void | at_type (typeNode *the_type, Order ord) |
virtual void | at_prim (primNode *the_prim, Order ord) |
virtual void | at_tdef (tdefNode *the_tdef, Order ord) |
virtual void | at_ptr (ptrNode *the_ptr, Order ord) |
virtual void | at_array (arrayNode *the_array, Order ord) |
virtual void | at_func (funcNode *the_func, Order ord) |
virtual void | at_sue (sueNode *the_sue, Order ord) |
virtual void | at_struct (structNode *the_struct, Order ord) |
virtual void | at_union (unionNode *the_union, Order ord) |
virtual void | at_enum (enumNode *the_enum, Order ord) |
virtual void | at_suespec (suespecNode *the_suespec, Order ord) |
virtual void | at_expr (exprNode *the_expr, Order ord) |
virtual void | at_index (indexNode *the_index, Order ord) |
virtual void | at_const (constNode *the_const, Order ord) |
virtual void | at_id (idNode *the_id, Order ord) |
virtual void | at_binary (binaryNode *the_binary, Order ord) |
virtual void | at_unary (unaryNode *the_unary, Order ord) |
virtual void | at_cast (castNode *the_cast, Order ord) |
virtual void | at_comma (commaNode *the_comma, Order ord) |
virtual void | at_ternary (ternaryNode *the_ternary, Order ord) |
virtual void | at_call (callNode *the_call, Order ord) |
virtual void | at_initializer (initializerNode *the_initializer, Order ord) |
virtual void | at_stmt (stmtNode *the_stmt, Order ord) |
virtual void | at_block (blockNode *the_block, Order ord) |
virtual void | at_basicblock (basicblockNode *the_basicblock, Order ord) |
virtual void | at_exprstmt (exprstmtNode *the_exprstmt, Order ord) |
virtual void | at_target (targetNode *the_target, Order ord) |
virtual void | at_label (labelNode *the_label, Order ord) |
virtual void | at_case (caseNode *the_case, Order ord) |
virtual void | at_selection (selectionNode *the_selection, Order ord) |
virtual void | at_if (ifNode *the_if, Order ord) |
virtual void | at_switch (switchNode *the_switch, Order ord) |
virtual void | at_loop (loopNode *the_loop, Order ord) |
virtual void | at_while (whileNode *the_while, Order ord) |
virtual void | at_do (doNode *the_do, Order ord) |
virtual void | at_for (forNode *the_for, Order ord) |
virtual void | at_jump (jumpNode *the_jump, Order ord) |
virtual void | at_goto (gotoNode *the_goto, Order ord) |
virtual void | at_continue (continueNode *the_continue, Order ord) |
virtual void | at_break (breakNode *the_break, Order ord) |
virtual void | at_return (returnNode *the_return, Order ord) |
virtual void | at_attrib (attribNode *the_attrib, Order ord) |
virtual void | at_operand (operandNode *the_oper, Order ord) |
virtual void | at_conditiongoto (conditiongotoNode *the_condgoto, Order ord) |
virtual void | at_threeAddr (threeAddrNode *the_3addr, Order ord) |
virtual void | at_text (textNode *the_text, Order ord) |
Private Attributes | |
Order | _order |
The order in which AST Nodes should be visited. | |
Depth | _depth |
Which Nodes in the AST should be visited. |
A Walker is a functional class that traverses an abstract syntax tree, and performs some function at each of its Nodes. At each Node, the function it performs depends on the class of the Node.
Corresponding to each class in the Node hierarchy, Walker defines an "at_" method. To specify the function that should be performed for Nodes of a particular class, create a subclass of Walker that overrides the "at_" method corresponding to that class. By default, the "at_" methods perform no action. Thus, a Walker subclass only needs to override the "at_" methods corresponding to Node types that are relevant to that walker.
As the AST is traversed, the most specific "at_" method that has been defined for each Node will be called on that Node. For example, if a Walker subclass overrides "at_decl()", but not "at_subdecl()," then the "at_decl()" method wil be called for all declNodes and subDeclnodes encountered in the AST. However, if a Walker subclass overrides both "at_decl()" and "at_subdecl," then the "at_decl()" method will be called for all declNodes encountered in the AST, and the "at_subdecl()" method will be called for all subdeclNodes encountered in the AST. If you wish for both "at_subdecl()" and "at_decl()" to be called for subdeclNodes, then you should explicitly call the "at_decl()" method from "at_subdecl()."
As the walker traverses the AST, the "at_" methods for a Node can be called before its children have been visited, after its children have been visited, or both before and after its children have been visited. When the "at_" methods for a Node are called before its children, they are said to be called in "preorder." When the "at_" methods for a Node are called after its children, they are said to be called in "postorder." If "at_" methods are called both in preorder and in postorder, then the preorder call will always preceed the postorder call.
When a new Walker is created, the order(s) that Nodes are visited in should be specified. In general, all instances of a given subclass of Walker will visit Nodes in the same order. However, it may occasionally be useful to specify different orders for two different instances of the same subclass of Walker.
New instances of Walker can also specify the "depth" of the traversal. If the depth is "SubTree," then a Walker will visit the entire AST rooted at the Node that it is called on. If the depth is "NodeOnly," then the Walker will only call the "at_" method for Node it is called on, and not for any of its sub-Nodes. Thus, a Walker with a depth of NodeOnly functions as if it were a Visitor. If a Walker subclass will always use a depth of NodeOnly, then it should be written as a Visitor instead. The depth value is provided because it can occasionally be useful to use a Walker subclass that was designed to traverse an entire AST to simply visit one Node. In this case, you can simply instantiate the Walker subclass with a depth of NodeOnly.
It is possible for a Walker to modify the fields of the Nodes it visits. However, Walkers should not modify the structure of the AST that is being traversed. In other words, Walkers should only modify Node fields that do not contain sub-Nodes. If the structure of the traversed AST needs to be modified as it is traversed, then a Changer should be used instead of a Walker.
Currently, Walkers traverse the AST in a depth-first order. Preorder calls to the "at_" methods are called before descending into a Node's children, and postorder calls to the "at_" method are called after returning from the children in the traversal. At the leaves, the postorder calls to the "at_" methods immediately follow the preorder calls. However, this ordering is subject to change, and should not be relied upon. The only aspects of the AST traversal ordering which are guaranteed are:
Walkers should never be used to traverse ASTs containing cycles; since they detect no mechanism to detect cycles, this would cause an infinite loop.
To use a walker "my_walker" to traverse an AST rooted at "my_node," use the code:
my_node->walk(my_walker);
Definition at line 142 of file walker.h.
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Which Nodes in the AST tree should be visited.
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The order in which AST Nodes should be visited.
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Create a new instance of a Walker. This constructor is usually called by a subclass.
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Reimplemented in TreeChecker, and print_walker. Definition at line 254 of file walker.h. References at_type(). |
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Reimplemented in print_walker. Definition at line 365 of file walker.h. References at_stmt(). |
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Reimplemented in print_walker, LivenessWalker, LivenessComments, and reachingDefinitionsWalker. Definition at line 314 of file walker.h. References at_block(). |
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Reimplemented in gcWalker, id_lookup_walker, TreeChecker, and print_walker. Definition at line 287 of file walker.h. References at_expr(). |
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Reimplemented in scope_walker, and print_walker. Definition at line 311 of file walker.h. References at_stmt(). Referenced by at_basicblock(). |
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Reimplemented in ref_fix_walker, set_container_walker, TreeChecker, and print_walker. Definition at line 359 of file walker.h. References at_jump(). |
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Reimplemented in id_lookup_walker, Linker, ref_fix_walker, TreeChecker, and print_walker. Definition at line 302 of file walker.h. References at_expr(). |
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Reimplemented in ref_fix_walker, semcheck_walker, set_container_walker, TreeChecker, and print_walker. Definition at line 326 of file walker.h. References at_target(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 293 of file walker.h. References at_expr(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 296 of file walker.h. References at_expr(). |
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Reimplemented in TreeChecker, print_walker, LivenessWalker, and LivenessComments. Definition at line 371 of file walker.h. References at_goto(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 281 of file walker.h. References at_index(). |
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Reimplemented in ref_fix_walker, set_container_walker, TreeChecker, and print_walker. Definition at line 356 of file walker.h. References at_jump(). |
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Reimplemented in id_lookup_walker, name_mangle_walker, semcheck_walker, TreeChecker, ProcWalker, print_walker, has_struct_walker, and UnificationBasedPtr. Definition at line 233 of file walker.h. References at_def(). Referenced by at_subdecl(). |
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Definition at line 230 of file walker.h. References at_node(). |
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Reimplemented in print_walker. Definition at line 344 of file walker.h. References at_loop(). |
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Reimplemented in enum_value_walker, and id_lookup_walker. Definition at line 269 of file walker.h. References at_sue(). |
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Definition at line 275 of file walker.h. References at_node(). Referenced by at_binary(), at_call(), at_cast(), at_comma(), at_index(), at_initializer(), at_operand(), at_ternary(), and at_unary(). |
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Reimplemented in semcheck_walker, and print_walker. Definition at line 317 of file walker.h. References at_stmt(). |
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Reimplemented in semcheck_walker, TreeChecker, and print_walker. Definition at line 347 of file walker.h. References at_loop(). |
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Reimplemented in scope_walker, TreeChecker, print_walker, and has_struct_walker. Definition at line 257 of file walker.h. References at_type(). |
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Reimplemented in goto_label_walker, fix_goto_walker, ref_fix_walker, TreeChecker, ProcWalker, and print_walker. Definition at line 353 of file walker.h. References at_jump(). Referenced by at_conditiongoto(). |
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Reimplemented in callGraph, id_lookup_walker, Linker, name_mangle_walker, ref_fix_walker, TreeChecker, and print_walker. Definition at line 284 of file walker.h. References at_index(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 332 of file walker.h. References at_selection(). |
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Definition at line 278 of file walker.h. References at_expr(). Referenced by at_const(), and at_id(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 305 of file walker.h. References at_expr(). |
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Definition at line 350 of file walker.h. References at_stmt(). Referenced by at_break(), at_continue(), at_goto(), and at_return(). |
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Reimplemented in goto_label_walker, name_mangle_walker, TreeChecker, ProcWalker, and print_walker. Definition at line 323 of file walker.h. References at_target(). |
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Reimplemented in semcheck_walker, set_container_walker, TreeChecker, and init_flowproblem_walker. Definition at line 338 of file walker.h. References at_stmt(). Referenced by at_do(), at_for(), and at_while(). |
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Reimplemented in gcWalker, goto_label_walker, set_container_walker, sue_complete_walker, TreeChecker, and df_number_walker. Definition at line 223 of file walker.h. Referenced by at_def(), at_expr(), at_stmt(), at_text(), at_type(), and at_unit(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 368 of file walker.h. References at_expr(). |
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Reimplemented in print_walker. Definition at line 245 of file walker.h. References at_type(). |
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Reimplemented in vcgWalker, id_lookup_walker, name_mangle_walker, ref_fix_walker, scope_walker, set_container_walker, TreeChecker, UnitWalker, print_walker, init_flowproblem_walker, LivenessWalker, LivenessComments, reachingDefinitionsWalker, and UnificationBasedPtr. Definition at line 239 of file walker.h. References at_def(). |
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Reimplemented in print_walker. Definition at line 251 of file walker.h. References at_type(). |
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Reimplemented in ref_fix_walker, semcheck_walker, set_container_walker, TreeChecker, print_walker, LivenessWalker, and LivenessComments. Definition at line 362 of file walker.h. References at_jump(). |
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Reimplemented in semcheck_walker. Definition at line 329 of file walker.h. References at_stmt(). Referenced by at_if(), and at_switch(). |
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Reimplemented in init_flowproblem_walker, and LivenessWalker. Definition at line 308 of file walker.h. References at_node(). Referenced by at_attrib(), at_block(), at_exprstmt(), at_jump(), at_loop(), at_selection(), at_target(), and at_threeAddr(). |
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Definition at line 263 of file walker.h. References at_sue(). |
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Definition at line 236 of file walker.h. References at_decl(). |
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Reimplemented in id_lookup_walker, print_walker, and has_struct_walker. Definition at line 260 of file walker.h. References at_type(). Referenced by at_enum(), at_struct(), and at_union(). |
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Reimplemented in scope_walker, semcheck_walker, sue_complete_walker, print_walker, and UnificationBasedPtr. Definition at line 272 of file walker.h. References at_type(). |
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Reimplemented in set_container_walker, TreeChecker, ProcWalker, print_walker, and init_flowproblem_walker. Definition at line 335 of file walker.h. References at_selection(). |
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Reimplemented in init_flowproblem_walker. Definition at line 320 of file walker.h. References at_stmt(). Referenced by at_case(), and at_label(). |
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Reimplemented in id_lookup_walker, ref_fix_walker, TreeChecker, and print_walker. Definition at line 248 of file walker.h. References at_type(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 299 of file walker.h. References at_expr(). |
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Reimplemented in print_walker. Definition at line 377 of file walker.h. References at_node(). |
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Reimplemented in Linker, TreeChecker, print_walker, LivenessWalker, LivenessComments, and UnificationBasedPtr. Definition at line 374 of file walker.h. References at_stmt(). |
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Reimplemented in TreeChecker. Definition at line 242 of file walker.h. References at_node(). Referenced by at_array(), at_func(), at_prim(), at_ptr(), at_sue(), at_suespec(), and at_tdef(). |
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Reimplemented in TreeChecker, and print_walker. Definition at line 290 of file walker.h. References at_expr(). |
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Definition at line 266 of file walker.h. References at_sue(). |
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Reimplemented in gcWalker, TreeChecker, print_walker, and UnificationBasedPtr. Definition at line 227 of file walker.h. References at_node(). |
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Reimplemented in print_walker. Definition at line 341 of file walker.h. References at_loop(). |
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Return which Nodes of an AST should be visited. A value of SubTree specifies that the entire AST should be traversed. A value of NodeOnly specifies that only the root Node in the AST should be visited. Definition at line 211 of file walker.h. References _depth. |
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Return the order in which Nodes of an AST should be visited. Nodes can be visited before their children (Preorder), after their children (Postorder), or both (Both). Definition at line 203 of file walker.h. References _order. Referenced by df_number_walker::at_node(). |
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Which Nodes in the AST should be visited.
Definition at line 166 of file walker.h. Referenced by depth(). |
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The order in which AST Nodes should be visited.
Definition at line 163 of file walker.h. Referenced by order(). |
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